1. Field of the Invention
The present invention relates to an organic electroluminescent device and its method of manufacture, and more particularly, the present invention relates to an organic electroluminescent device that can prevent leakage current, short circuits, and color mixing between pixels and its method of manufacture.
2. Description of the Related Art
In general, organic electroluminescent devices are display devices that realize an image using light emitted by combining holes supplied from an anode electrode with electrons supplied from a cathode electrode in an organic emitting material layer formed between the anode electrode and the cathode electrode. Due to superior display characteristics such as wide viewing angle, rapid response time, low manufacturing costs, and high contrast, organic electroluminescent devices are expected to be the next generation of flat panel display devices.
Organic electroluminescent devices can be divided into Passive Matrix (PM) devices and Active Matrix (AM) devices. A PM organic electroluminescent device has a structure in which anode electrodes and cathode electrodes are arranged in a matrix, and an AM organic electroluminescent device has a structure in which an anode electrode, a plurality of Thin Film Transistors (TFTs), and capacitors are arranged in each pixel. Also, organic electroluminescent devices can be divided into top emission devices and bottom emission devices according to the direction of light emission from an organic emitting material layer.
FIG. 1 is a plan view of a PM organic electroluminescent device, and FIG. 2 is a cross-sectional view taken along the line II-II′ of FIG. 1.
Referring to FIGS. 1 and 2, a plurality of anode electrodes 12 are formed in a stripe shape on a substrate 10. Banks 15 that define pixels by exposing predetermined regions of the anode electrodes 12 are also formed on the substrate 10. The banks 15 are usually formed of an organic material. In the pixels defined by the banks 15, Hole Transporting Layers (HTLs) 21 are formed to contact the anode electrodes 12, and organic Emitting Material Layers (EMLs), each emitting a predetermined color, for example, a red light emitting layer 20R, a green light emitting layer 20G, and a blue light emitting layer 20B, are formed on each upper surface of the HTLs 21. The organic EMLs having the same color are formed along the direction of the anode electrodes 12. The HTLs 21 and the organic EMLs 20R, 20G, and 20B can be formed using a spin coating method, a dispensing method, or an ink jet method. A plurality of cathode electrodes 32 are formed in stripe shapes on upper surfaces of the organic EMLs 20R, 20G, and 20B and the banks 15. The cathode electrodes 32 cross the anode electrodes 12.
However, in the organic electroluminescent device having the above structure, the banks 15 are formed of an organic material having a large contact angle with respect to materials which form the HTLs 21 and the organic EMLs 20R, 20G, and 20B, and thus, the HTLs 21 and the organic EMLs 20R, 20G, and 20B are thin at the edges of the pixels. Accordingly, when the cathode electrodes 32 contact the HTLs 21, a leakage current can occur. Furthermore, when the cathode electrodes 32 contact the anode electrodes 12, short circuits can occur. Also, when the HTLs 21 and the organic EMLs 20R, 20G, and 20B are formed using a dispensing method, a disconnection of the HTLs 21 or the organic EMLs 20R, 20G, and 20B can occur.